November 23, 1917] 



SCIENCE 



517 



The data also permit of the proper choice 

 of substitutes for woods which have become 

 scarce or unobtainable. Here again the air- 

 plane may be cited, since the supplies of some 

 woods ordinarily used in airplane construction 

 are insufficient to meet the present building 

 program of the United States and its allies. 



Among the relations between mechanical 

 and physical properties of wood for which laws 

 have been obtained are static bending-specific 

 gravity, impact bending-specific gravity, com- 

 pression parellel to grain-specific gravity, 

 compression perpendicular to grain-specific 

 gravity, static bending-moisture content; im- 

 pact bending-moisture content, compression 

 parallel to grain-moisture content, compres- 

 sion perpendicular to grain-moisture content, 

 shrinkage-moisture content. 



The bulletin, the authors of which are J. 

 A. ISTewlin and Thomas R. C. "Wilson, is en- 

 titled " Mechanical Properties of Woods 

 Grown in the United States," and is No. 556 

 in the Department of Agriculture series. 



SPECIAL ARTICLES 

 A CONVENIENT NERVE HOLDER 



For several years past in this laboratory 

 experiments on chemical stimulation have 

 formed a part of the routine students' work 

 on the physiology of muscle and nerve. In 

 these experiments we have used a nerve holder 



Fig. 1. 



which has proved so simple and convenient 

 that it seems desirable to suggest it to others. 

 In its first form it consisted merely of a thin 

 watch-glass 45 to 50 mm. in diameter, 

 cemented by sealing-wax to the flattened end 

 of a piece of J inch lead wire 12 inches long. 

 If the muscle of a gastrocnemius-sciatic 

 preparation is mounted on a muscle lever, the 

 edge of the watch-glass may be brought very 

 near to the muscle and the whole nerve may 

 be allowed to lie in the liquid to be applied. 



as for example, a solution of sodium citrate or 

 barium chloride. 



The construction is so simple, requiring no 

 special skill and only a few minutes of time, 

 that it was used in this way for two or three 

 years. Later, Mr. L. A. Eay, technician, de- 

 vised the following more permanent construc- 

 tion. A small bit of glass rod is fused to the 

 bottom of the watch-glass. The rod is then 

 melted and pulled in two at a point about J to 

 i inch from the bottom of the glass, and is 

 held in the flame till a small knob forms on 

 the end. A hole is punched in the flattened 

 end of the lead rod, the glass rod is inserted 

 and the joint made fast with cement. The 

 knob on the end of the glass is held firmly in 

 place by the cement. The accompanying figure 

 of a section of watch-glass and rod will make 

 the whole arrangement perfectly obvious. 

 S. S. Maxwell 



Rudolph Spreckels Phtsioloqical Laboratoby, 



TJNIVEESITT of CALIirOENIA 



THE URINE OF THE HORNED LIZARD 



Vauqijelin,^ in reporting the first analysis of 

 reptilian urine, in 1822, stated that it was com- 

 posed almost entirely of uric acid, and since 

 that time this fact has been interpreted by 

 various observers as an adaptation to the con- 

 ditions of life in arid regions, where animals 

 obtain their only external water supply in 

 very limited quantities in the food substances, 

 as this type of nitrogenous excretion involves 

 practically no water loss. The reptiles of arid 

 regions have been known for some time to ex- 

 crete practically all of their waste nitrogen in 

 the form of uric acid and its salts, while, on 

 the other hand, birds and aquatic and semi- 

 aquatic reptiles may excrete considerable 

 amounts of urea. 



1 Vauquelin, Louis Nicolas, "Examen des ex- 

 crgmens des serpens que 1 'on fait voir en ce moment 

 a Paris, Eue Saint-Nicaise, " Annates de CMmie ei 

 de Pliisique. S'"e Serie, Tome 21, p. 440, 1822. 

 Two boas, species not stated, were the source of 

 the urine examined in this case. Uric acid had also 

 been associated with reptiles as early as 1793, when 

 a "pasty deposit" found in the bladder of a tor- 

 toise by Vicq-d'Azyr was found to contain this 

 substance. 



